Conventionally, as a brake included in a transmission of this type, a brake has been known having: one piston that is slidable in a case or a cylinder coupled to the case, and causes friction members and disk plates to engage with and disengage from each other; a first oil pressure chamber provided to the piston; a second oil pressure chamber provided to the piston separately from the first oil pressure chamber; and a return spring that continuously biases the piston toward the first and the second oil pressure chambers (see Patent Documents 1 and 2, for example). In such a brake, engagement oil pressure (hydraulic oil) is supplied to either one of the first and the second oil pressure chambers when the torque share becomes relatively low, and the engagement oil pressure is supplied to both of the first and the second oil pressure chambers when the torque share becomes relatively high.